How to stay warm without burning through your power bill
You have the heater running. The room still feels cold. Where is all that warmth going?
If your windows are bare, the answer is: through the glass.
Glass is the weakest thermal point in most Australian homes. Uncovered windows can lose up to 40% of a room’s heat overnight, which is why your heater never seems to switch off in July, and your bill arrives looking like a phone number.
Closed thermal blinds change that maths. Here is how, and what to look for if you want them to actually work.
Where your heat is actually escaping
Walls, ceilings, and floors are usually insulated. They slow the transfer of heat reasonably well. Glass does not. A single-pane window has roughly the insulation value of a thin sheet of plywood, meaning anything you heat in that room is racing toward the cold side of the glass and disappearing into the night.
Even double-glazed windows leak heat at a measurable rate. They reduce the loss, but they do not stop it.
The point of a thermal blind is to put a second barrier in front of the glass and trap a layer of still air between them. Still air is one of the cheapest insulators going. Trap enough of it in the right place and your room holds its heat for hours longer.
Do blinds help hold heat in?
Yes, but only if they seal.
A standard roller blind that hangs in front of the window will block some light and reduce some draught, but warm air will leak around the sides, top, and bottom and rush toward the cold glass anyway. The blind itself is not the problem. The gaps are.
Properly thermal blinds solve this with three things working together:
- A foam-backed or insulating fabric. Thicker than a standard roller fabric. Reflects radiant heat back into the room.
- Side channels that grip the window frame. Stops air bypassing the blind through the side gaps.
- Brush seals at the top and bottom. Closes the last two gaps so the trapped air cannot circulate.
When all three are in place, you have a sealed pocket of still air against the glass. That is the insulator. The fabric on its own is doing maybe a third of the work, the seal does the rest.
Which blinds are best for keeping heat in?
In the Australian market, two formats genuinely insulate:
Honeycomb (cellular) blinds. Their fabric folds into hexagonal cells that trap air inside the cell wall structure. They have been the default recommendation for thermal performance for years. Downside: the cellular pattern shows whether the blind is up or down, and most styles let pinpoints of light through.
Sealed roller blackout blinds with side channels. A foam-backed blackout fabric in a roller cassette, running inside aluminium side channels with brush seals top and bottom. Same physics, sealed pocket of still air, different geometry. Trade-off: you get a clean roller look and 100% blockout, no light bleed.
The two perform comparably on insulation when the seal is good. We make the second kind because the seal is what does the work, and we want our customers to keep both the insulation and a clean window line.
What does not insulate effectively: standard roller blinds without side channels, vertical blinds, venetian blinds, and curtains without pelmets. They all let air leak around the edges.
What blinds keep your house warm: the things that actually matter
Before you buy any thermal blind, ours or anyone else’s, check it has these three things. Without all three, the blind will block light but it will not retain heat.
- A blockout fabric, ideally foam-backed. Look for “100% blockout” or “soft foam backed” in the spec sheet.
- Side channels. They should grip the window architrave or sit inside the reveal. Without them, all the warm air leaks past the sides.
- A sealed top and bottom. A pelmet, brush seal, or recessed cassette. Anything that stops air rolling over the top of the blind and circulating against the cold glass.
If a blind has all three, it will retain heat. If it is missing one, you are buying a light blocker, not a thermal blind. The marketing copy and the engineering are not the same thing.
How much can you actually save?
Effective insulation across a whole household, including window coverings, can reduce heating and cooling costs by up to 45% according to energy.gov.au. Thermal blinds do not deliver all of that on their own, but they close one of the largest leaks in the average home.
Realistic effects you can expect:
- Bedrooms hold their temperature longer overnight, so the heater cycles less.
- Living rooms with large or west-facing glazing stop swinging cold late afternoon.
- The lag between turning the heater off and the room going cold gets longer.
- You stop hearing the reverse-cycle kick on every 20 minutes.
The biggest impact is in rooms with the most glass and the worst insulation elsewhere. A bedroom with a single large window will feel different the first night the blinds are sealed. A small bathroom with a tiny pane will not change much.
Rooms to prioritise first
If you are buying a few at a time, do these in this order:
- Bedrooms. You want to hold heat overnight, and you want the room dark. Thermal blackout blinds do both at once.
- Living rooms with west-facing or large windows. These are the worst leakers and the biggest payoff.
- Any room with single-pane glass. Older homes especially. The blind is doing the work the window cannot.
- The room you sit in at night. Where you lose the most comfort to a cold window after dinner.
Bathrooms and laundries are lowest priority. They are not heated for long, and the windows are usually small.
You can install them yourself
Every Coverlight thermal blackout blind is built to install without a trade. You measure your window using our DIY measuring guide. You order online and configure the fabric, frame, and drive. Two screws each side, the blind clicks into the brackets, the side channels seal it shut. Most rooms take 15 to 20 minutes start to finish, full instructions in our installation guide.
No installer fee. No three-week wait for a booking. No markup chain.
Stop heating the outside of your house
You do not need to live with cold rooms in winter, and you do not need to keep paying for heat that escapes overnight. A properly sealed thermal blackout blind in your bedrooms and main living areas will make a measurable difference within a single billing cycle.
